The proposed program represents a multidisciplinary series of fundamental investigations into the interrelationships between the central nervous system, monoamine neurons and arterial hypertension. The broad objectives of these studies are to: (a) identify and characterize the physiology, the anatomy and the cardiovascular actions of regions of the brain which serve to integrate the reflex control of the arterial pressure; (b) develop models of stable and labile arterial hypertension in animals through perturbation of these central neural mechanisms which maintain circulatory homeostasis, and to examine the role of central monoamine neurons in this control; (c) analyze in detail the neurochemistry of those neural systems in the brain which synthesize, store and release the monoamine neurotransmitters, including the catecholamines norepinephrine, dopamine and epinephrine and the indole serotonin; and (d) investigate the cellular biology of the monoamine systems in the brain which serve in the regulation of arterial pressure particularly with regard to their ultrastructure and plasticity. BIBLIOGRAPHIC REFERENCES: Nathan, M. A. and Reis, D. J.: Chronic labile hypertension produced by lesions of the nucleus tractus solitarii in the cat. Circ. Res. 40: 72-81, 1977. Kumada, M., Dampney, R. A. L., and Reis, D. J.: The trigeminal depressor response: A novel vasodepressor response originating from the trigeminal system. Brain Res., 119: 305-326, 1977.